Optical metrology system and method employing laser-server supplying laser energy to distributed slave metrology heads

Abstract

A metrology system has one or more central ‘metrology servers’ and one or more ‘metrology slaves’ The server delivers metrology ‘pump/probe’ signals to multiple slave systems allowing a reduction in the number of high-cost metrology components in the master system. In certain cases, multiple metrology components in the ‘master’ system may provide redundancy while still maintaining a beneficial cost benefit. Reliability can also be improved by using multiple lasers and multiple delay paths with a cross-point switch between them. If one sub-system goes down, the system may ‘serialize’ metrology operations and thereby maintain all systems running, although at somewhat of a reduced throughput. An important element of this invention is grouping all or most of the costly components in a centralized laser server, and issuing pump-probe pulse pairs to remote metrology heads through a light pipe or other conveyance, such as optical fiber. The remote metrology heads can thus be reduced in cost and complexity.

What is claimed is:  
     
       1. An optical metrology system, comprising: 
       a metrology master system comprising at least one source of optical sample measurement energy;  
       a plurality of metrology slave systems where measurements are performed on samples each comprised of a semiconductor material; and  
       a metrology conveyance system connected between said master system and said plurality of slave systems, said metrology conveyance system delivering said optical sample measurement energy to individual ones of said plurality of slave systems for application to said samples.  
     
     
       2. A system as in  claim 1 , wherein said master system comprises a plurality of lasers of the same type. 
     
     
       3. A system as in  claim 1 , wherein said master system comprises a plurality of lasers of different types. 
     
     
       4. A system as in  claim 1 , wherein said conveyance system delivers pump pulses. 
     
     
       5. A system as in  claim 1 , wherein said conveyance system delivers pump/probe pulse pairs. 
     
     
       6. A system as in  claim 1 , wherein said conveyance system is comprised of a conduit providing a path through at least one of the air or another environment, where the other environment comprises at least one of vacuum or a selected gas. 
     
     
       7. A system as in  claim 1 , wherein said conveyance system is comprised of optical fiber. 
     
     
       8. A system as in  claim 1 , wherein said metrology conveyance system is comprised of a conduit providing a path through the air and an adaptive optics system for performing wavefront shaping. 
     
     
       9. A system as in  claim 1 , wherein said metrology conveyance system is comprised of a conduit providing a path through the air and an adaptive optics system for performing vibration cancellation. 
     
     
       10. A system as in  claim 1 , wherein said metrology slave systems comprise optical detection systems for detecting probe light that is reflected from or transmitted through a sample. 
     
     
       11. A system as in  claim 1 , wherein said metro logy master system comprises an optical detection system for detecting probe light that is reflected from or transmitted through a sample, the probe light being delivered through said metrology conveyance system from said metrology slave systems back to said metrology master system. 
     
     
       12. A method for performing optical metrology, comprising steps of: 
       operating a metrology master system having at least one source of optical sample measurement energy to generate an optical beam;  
       providing a plurality of metrology slave systems where measurements are performed on samples each comprised of a semiconductor material; and  
       conveying said optical beam through a metrology conveyance system connected between said master system and said plurality of slave systems, said metrology conveyance system delivering said optical beam for use as sample measurement energy at said plurality of metrology slave systems.  
     
     
       13. A method as in  claim 12 , wherein said master system comprises a plurality of lasers of the same type. 
     
     
       14. A method as in  claim 12 , wherein said master system comprises a plurality of lasers of different types. 
     
     
       15. A method as in  claim 12 , wherein said metrology conveyance system conveys pump pulses or pump/probe pulse pairs. 
     
     
       16. A method as in  claim 12 , wherein said conveyance system is comprised of a conduit providing a path through at least one of the air or another environment, where the other environment comprises at least one of vacuum or a selected gas. 
     
     
       17. A method as in  claim 12 , wherein said conveyance system is comprised of optical fiber. 
     
     
       18. A method as in  claim 16 , wherein said conveyance system is further comprised of an adaptive optics system for performing at least one of wavefront shaping or vibration cancellation. 
     
     
       19. An method as in  claim 12 , wherein said metrology slave systems comprise optical detection systems for detecting probe light that is reflected from or transmitted through a sample. 
     
     
       20. An method as in  claim 12 , wherein said master metrology system comprises an optical detection system for detecting probe light that is reflected from or transmitted through a sample, the probe light being delivered through said metrology conveyance system from said metrology slave systems back to said metrology master system. 
     
     
       21. A distributed optical metrology system for characterizing samples comprised of integrated circuits, comprising: 
       a source of optical sample measurement energy;  
       a plurality of measurement stations where samples are characterized; and  
       a conveyance system connected between said source and individual ones of said plurality of measurement stations, said conveyance system delivering said optical sample measurement energy to individual ones of said plurality of measurement stations for application to said samples.  
     
     
       22. A system as in  claim 21 , wherein said conveyance system is further comprised of an adaptive optics system for performing at least one of wavefront shaping or vibration cancellation. 
     
     
       23. A system as in  claim 21 , wherein said samples are characterized by measurement of a film disposed on a surface of the sample. 
     
     
       24. A distributed optical metrology system for characterizing samples comprised of semiconductor wafers, comprising: 
       at least one source of optical sample measurement energy;  
       a plurality of measurement stations where samples are characterized; and  
       an optical conveyance system connected between said source and individual ones of said plurality of measurement stations, said conveyance system delivering pump pulse and probe pulse pairs derived from said at least one source to individual ones of said plurality of measurement stations for application to said samples.  
     
     
       25. A system as in  claim 24 , wherein said conveyance system is further comprised of an adaptive optics system for performing at least one of wavefront shaping and vibration cancellation. 
     
     
       26. A system as in  claim 24 , further comprising, at each of said measurement stations, an optical detector for detecting probe pulses that are one of reflected from or transmitted through a sample located at said measurement station. 
     
     
       27. A system as in  claim 24 , further comprising an optical detector for detecting probe pulses that are one of reflected from or transmitted through a sample located at each of said measurement stations. 
     
     
       28. A system as in  claim 24 , where said optical conveyance system is bidirectional for conveying probe pulses that are one of reflected from or transmitted through a sample located at said measurement station back to at least one optical detector that is separate from said plurality of measurement stations. 
     
     
       29. A system as in  claim 24 , where said pump pulses are modulated, and wherein corresponding probe pulses are variably delayed with respect to said pump pulses.